Sony TC-765 - Control, Muting, and Bias Oscillator Circuits

TC-765 |
12.
STOP Circuit (Refer to Fig. 14)
(Shut-Off Circuit)
When the tape has finished winding, or when
slack, tension arm micro-switch (S605, 606) is
closed adding 24V to Q723 through R756.
(Path @)
Because of this, Q723 is turned ON activating
the IC701 input.
When AC is ON, Q722 slowly goes to the ON
state as determined by time constant of R751
and C717. (Refer to TIMER-activated opera-
tion)
To supplement this, while Q722 is OFF, Q723
is ON and the STOP input of IC701 is activated.
(Path @))
S605 S606
shut off shut off
(supply reel) (take-up reel)
=a tape oe
tape ="; wound 82
“~~ TC input
STOP
C7I7
13.
TIMER-Activated Operation (Refer to Fig. 15)
With TIMER switch (S603) ON, when the
POWER switch (S604) is turned on, the voltage
at point @ supplied through D726 and Bt
voltage (+24V) rise after 0.2 to 0.5 seconds.
At this time, C717 is charged through R751
and the charged voltage turns on zener diode
D768 after 5 seconds determined by a time
constant of R751 and C717, and then turns on
Q722.
As a result of 2., the (+) side of C719 becomes
-5 to -6V and passing through S603, D766 and
767 are turned ON to produce the record and
forward signals for the Record or Playback
modes,
(The circuit containing D726, 727, C716 and R750
makes C717 quickly discharged, when the power
supply is turned off.)
(pomer supply oe)
solenoid hold etc.
Fig. 14
$603
: TIMER
OFF > ON
0767 “
to input of
an function button p (Forward)
D766 “
to input of
ON function button ¢ (Record)
12V
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